The present invention relates to a magnetic-pole position detecting apparatus for a synchronous motor capable of detecting a magnetic-pole position of a synchronous motor easily, securely and with high precision.
In order to efficiently control a synchronous motor, it has been a conventional practice to detect magnetic-pole positions of a rotor of the synchronous motor. As a method for detecting a magnetic-pole position of the synchronous motor, there has been a method of directly detecting an electric angle (a magnetic-pole position) of the rotor by using a position detector, like an encoder. However, in order to detect directly a rotation angle of the rotor, it is neccessary to add to the synchronous motor a sensor exclusively used for detecting a magnetic-pole position, like a position detector. This has drawbacks in that the scale of the apparatus becomes large which further leads to unsatisfactory economics of the apparatus.
Therefore, there has been proposed an apparatus that detects a magnetic-pole position of a synchronous motor without using a position detector (reference Japanese Patent Application (Laid-Open) No. 7-177788). FIG. 24 is a diagram showing a schematic configuration of a conventional magnetic-pole position detecting apparatus for a synchronous motor that does not use a position detector. In FIG. 24, a synchronous motor 1 has a permanent-magnet type rotor, and has a three-phase winding of U-phase, V-phase and W-phase. An arithmetic section 102 outputs a voltage vector command V to a circuit section 3, and outputs a trigger signal Tr to a detection section 4. The circuit section 3 applies a voltage to each phase of the synchronous motor 1 based on the input voltage vector command V. The detection section 4 detects a current of each phase at a rise timing of the trigger signal Tr, and outputs a detection current Di to the arithmetic section 102. The arithmetic section 102 calculates a magnetic-pole position xcex8 of the rotor based on the input detection current Di, and outputs a calculated result.
FIG. 25 is a diagram showing a detailed structure of the circuit section 3. In FIG. 25, the circuit section 3 has semiconductor switches 5 to 10. Each pair of semiconductor switches 5 and 8, 6 and 9, and 7 and 10 respectively are connected in series. Each pair of semiconductor switches 5 and 8, 6 and 9, and 7 and 10 respectively are connected in parallel with a DC voltage source 11 that generates a phase potential Ed. An intermediate point Pu for connecting between the semiconductors 5 and 8 is connected to the U-phase of the synchronous motor 1. An intermediate point Pv for connecting between the semiconductors 6 and 9 is connected to the V-phase of the synchronous motor 1. An intermediate point Pw for connecting between the semiconductors 7 and 10 is connected to the W-phase of the synchronous motor 1. Each of the semiconductor switches 5 to 10 has a corresponding one of insulation gate type bipolar transistors (IGBT) Q1 to Q6 and a corresponding one of diodes D1 to D6 connected in parallel. The diodes are directed in sequence to a plus side of the DC voltage source 11. Agate signal to be applied to a gate of each of the IGBTs Q1 to Q6 forms a voltage vector command V, and this voltage vector command V turns off/off corresponding transistors of the IGBTs Q1 to Q6.
The voltage vector V has nine switching modes xe2x80x9c0xe2x80x9d to xe2x80x9c8xe2x80x9d, and the respective switching modes xe2x80x9c0xe2x80x9d to xe2x80x9c8xe2x80x9d are defined as follows based on combinations of the IGBTs Q1 to Q6 to be turned on.
Switching mode: Combination of the IGBTs Q1 to Q6 to be turned on
xe2x80x9c0xe2x80x9d: Nil
xe2x80x9c1xe2x80x9d: Q1, Q5, Q6
xe2x80x9c2xe2x80x9d: Q1, Q2, Q6
xe2x80x9c3xe2x80x9d: Q4, Q2, Q6
xe2x80x9c4xe2x80x9d: Q4, Q2, Q3
xe2x80x9c5xe2x80x9d: Q4, Q5, Q3
xe2x80x9c6xe2x80x9d: Q1, Q5, Q3
xe2x80x9c7xe2x80x9d: Q1, Q2, Q3
xe2x80x9c8xe2x80x9d: Q4, Q5, Q6
Voltage vectors V1 to V8 corresponding to the switching modes xe2x80x9c1xe2x80x9d to xe2x80x9c8xe2x80x9d have phase differences of 60 degrees respectively, with equal sizes as shown in FIG. 26. A size of the voltage vector V1 will be obtained here, as one example. As the voltage vector V1 corresponds to the switching mode xe2x80x9c1xe2x80x9d, the IGBTs Q1, Q5 and Q6 are turned on, and the IGBTs Q4, Q2 and Q3 are turned off. Therefore, a line voltage Vuv between the U-phase and the V-phase, a line voltage Vuv between the V-phase and the W-phase, and a line voltage Vwu between the W-phase and the U-phase are given by the following equations (1) to (3) respectively.
Vuv=Vuxe2x88x92Vv=Edxe2x80x83xe2x80x83(1) 
Vvw=Vvxe2x88x92Vw=0xe2x80x83xe2x80x83(2) 
Vwu=Vwxe2x88x92Vu=xe2x88x92Edxe2x80x83xe2x80x83(3) 
where, xe2x80x9cVuxe2x80x9d represents a phase of the U-phase (a potential of the intermediate point Pu), xe2x80x9cVvxe2x80x9d represents a phase of the V-phase (a potential of the intermediate point Pv), and xe2x80x9cVwxe2x80x9d represents a phase of the W-phase (a potential of the intermediate point Pw).
Further, from the equations (1) to (3), the potentials Vu to Vw are obtained as given by the following equations (4) to (6) respectively.
Vu=⅔*Edxe2x80x83xe2x80x83(4) 
Vv=xe2x88x92⅓*Edxe2x80x83xe2x80x83(5) 
Vw=xe2x88x92⅓*Edxe2x80x83xe2x80x83(6) 
Therefore, a direction of the voltage vector V1 becomes the direction of the U-phase as shown in FIG. 26. Further, a size |V1| of the voltage vector V1 is expressed as given by the following equation (7).
|V1=⅔*Edxe2x88x92⅓*Ed cos(120 degrees)xe2x88x92⅓*Edcos(240 degrees)=Edxe2x80x83xe2x80x83(7) 
Directions and sizes of other voltage vectors V2 to V6 can be obtained by carrying out similar calculations to those of the voltage vector V1. As shown in FIG. 26, directions of the voltage vectors V2 to V6 have phase differences of 60 degrees respectively sequentially from the U-phase, and their sizes become Ed. Further, the voltage vector V7 and V8 become voltage vectors having sizes 0 respectively as shown in FIG. 26.
Voltages corresponding to these voltage vectors V1 to V6 are applied to the U-phase, the V-phase and the W-phase of the synchronous motor 1 respectively. In this case, thedetection section 4 detects a current that flows through each phase at the rise timing of the trigger signal Tr. FIG. 27 is a block diagram showing a detailed structure of the detection section 4. In FIG. 27, current detectors 12 to 14 detect currents that flow through the U-phase, the V-phase and the W-phase respectively, and output the detection currents to output processing sections 15 to 17 respectively. The output processing sections 15 to 17 have sample holding circuits 15a to 17a and A/D converters 15b to 17b respectively. The sample holding circuits 15a to 17a hold samples of the current values detected by the current detectors 12 to 14 respectively at the rise timing of the trigger signal Tr input from the arithmetic section 102. The A/D converters 15b to 17b convert analog signals held by the sample holding circuits 15a to 17a into digital signals respectively, and output a current iu of the U-phase, a current iv of the V-phase, and a current iw of the W-phase respectively, which are collectively output as a detection current Di to the arithmetic section 2.
A relationship between the voltage vector command V, the trigger signal Tr and the detection current Di will be explained next with reference to a timing chart shown in FIG. 28. In FIG. 28, the arithmetic section 102 first sequentially outputs voltage vectors V0, V1, V0, V3, V0, V5, and V0 in this order to the circuit section 3 as the voltage vector command V, when the synchronous motor 1 is in the halted state and also when the current of each phase is zero. At the same time, the arithmetic section 102 outputs the trigger signal Tr to the detection section 4 immediately after finishing the application of each voltage vector. As explained above, the circuit section 3 sequentially applies the voltage vectors V0, V1, V0, V3, V0, V5, and V0 in this order to the synchronous motor 1 based on the voltage vector command V. The application time of each of the voltage vectors V1, V3 and V5 is set to a sufficiently short time within a time range in which the synchronous motor 1 is not magnetically saturated. The output processing sections 15 to 17 of the detection section 4 sample the currents of the respective phases, that is, the currents iu, iv and iw, at the rise timing of the trigger signal Tr, and output currents iu1 to iu3 of the U-phase, currents iv1 to iv3 of the V-phase, and currents iw1 to iw3 of the W-phase as detection results respectively to the arithmetic section 102. The current iu1 of the U-phase, the current iv1 of the V-phase and the current iw1 of the W-phase are the currents detected by the trigger signal Tr that is applied immediately after the voltage vector V1. The current iu2 of the U-phase, the current iv2 of the V-phase and the current iw2 of the W-phase are the currents detected by the trigger signal Tr that is applied immediately after the voltage vector V2. The current iu3 of the U-phase, the current iv3 of the V-phase and the current iw3 of the W-phase are the currents detected by the trigger signal Tr that is applied immediately after the voltage vector V3.
The magnetic-pole position xcex8 of the rotor of the synchronous motor 1 and the currents iu1, iv2 and iw3 have a relationship as shown in FIG. 29. Looking at a range of the magnetic-pole positions xcex8 from 0 to 18 degrees, the magnetic-pole positions xcex8 can be divided into six sections at every 30 degrees based on large-and-small relationships of the currents iu1, iv2 and iw3. The six divided regional sections of the magnetic-pole positions xcex8 are expressed as follows with section numbers attached to the respective sections.
Therefore, it is possible to obtain the magnetic-pole positions xcex8 at every 30 degrees based on the large-and-small relationships of the currents iu1, iv2 and iw3 when the magnetic-pole positions xcex8 are within the range from 0 to 180 degrees. In order to obtain a specific magnetic-pole position xcex8, this is calculated from the following equation (8).
0=(mxe2x88x921)xc3x9730+15+f(m)xc3x97(iavxe2x88x92im)xc3x97kxe2x80x83xe2x80x83(8) 
Among the current values of the currents iu1, iv2 and iw3 in each section of the 30 degree unit, any one of the currents iu1, iv2 and iw3 that has an intermediate current value is regarded as a straight line in this section. For example, the current iw3 in the section of the magnetic-pole positions xcex8 from 0 to 30 degrees is regarded as a straight line. A current iav is an average value of the currents iu1, iv2 and iw3. A current im is a current approximated by a straight line in this section number m, and a coefficient k is an inclination of this straight line. When section numbers are 1, 3 and 5, f(m)=1. When section numbers are 2, 4 and 6, f (m)=xe2x88x921.
A magnetic-pole position xcex80 can be specified as one-point magnetic-pole position xcex8 instead of a section within the range from 0 to 18 degrees based on this equation (8). As the magnetic-pole position xcex8 changes in the 180 degree period as shown in FIG. 29, the magnetic-pole position xcex8 is determined uniquely by using magnetic saturation forthe whole angles of 360 degrees.
For example, when the section number m is xe2x80x9c1xe2x80x9d, the magnetic-pole position xcex8 is either in the section of 0 to 30 degrees or in the section of 180 to 210 degrees. Therefore, it is not possible to uniquely specify the magnetic-pole position xcex8. In this case, the section of the magnetic-pole position xcex8 is selectively determined by applying the voltage vectors V1 and V4 having a long application time for generating a magnetic saturation is applied to the synchronous motor 1 as shown in FIG. 17.
More specifically, when there is no magnetic saturation generated, the absolute values of the currents iu4 and iu5 become equal. However, the magnetic flux generated when the voltage vectors V1 and V4 near the magnetic-pole position have been applied works in a direction to increase the magnetism of the magnetic flux of the rotor of the synchronous motor 1. Thus, when a magnetic saturation is generated, the inductance of the coil of the synchronous motor 1 decreases. Therefore, when a magnetic saturation has been generated, a current when the voltage vector V1 or V4 of a phase near the magnetic-pole position xcex8 has been applied has a larger value than a current when the voltage vector V1 or V4 of a phase 180 degrees different from the phase near the magnetic-pole position xcex8 has been applied.
As a result, when the magnetic-pole position xcex8 is either in the section of 0 to 30 degrees or in the section of 180 to 210 degrees, it is decided that the magnetic-pole position xcex8 is in the region of 0 to 30 degrees, when the size |iu4| of the current iu4 is larger than the size |iu5| of the current iu5. Thus, the magnetic-pole position xcex8 obtained from the equation (8) is output directly. When the size |iu4| of the current iu4 is smaller than the size |iu5| of the current iu5, it is decided that the magnetic-pole position xcex8 is in the section of 180 to 210 degrees. In this case, 180 degrees is added to the magnetic-pole position xcex8 obtained from the equation (8), and the result is output.
Similarly, when the section numbers m are xe2x80x9c2xe2x80x9d to xe2x80x9c6xe2x80x9d, the magnetic-pole positions xcex8 in the range of 0 to 180 degrees are obtained based on the equation (8). Thereafter, the voltage vectors corresponding to the section numbers are applied with a long application time for generating a magnetic saturation. Then, a relationship of the magnetic-pole positions of 180 degrees is decided using a large-and-small relationship of the absolute values of the voltage vectors. Thus, the magnetic-pole positions xcex8 are uniquely specified over the whole angles.
However, according to the above-described conventional magnetic-pole position detecting apparatus for a synchronous motor, as the magnetic-pole position xcex8 is first obtained within a large range of 180 degrees, it has been necessary to apply a voltage vector having an application time not sufficient for generating a magnetic saturation in the coil of the synchronous motor 1. As the currents iu1, iv2 and iw3 that are detected by the application of the voltage vector having an application time not sufficient for generating a magnetic saturation have small amplitudes, the signals of the currents iu1, iv2 and iw3 are easily affected by noise. Therefore, there is a potential that an erroneous amplitude is output. Further, there is a potential that a cancellation occurs when the A/D converters 15b to 17b convert analog signals into digital signals. Therefore, there is a case where it is not possible to detect the currents iu1, iv2 and iw3 in high precision. As a result, there has been a problem in that it is not possible to detect correctly the magnetic-pole positions xcex8.
Further, according to the above-described conventional magnetic-pole position detecting apparatus for a synchronous motor, as the magnetic-pole positions xcex8 are specified uniquely within the range from 0 to 360 degrees by using a magnetic saturation, two kinds of voltage vectors having an application time for generating a magnetic saturation have been applied. However, in this case, the influence of hysteresis characteristic of a coil is not taken into consideration. Actual amplitude of the detection current is influenced by the hysteresis characteristic of a coil of the synchronous motor, and is also dependent on the sequence of applying the voltage vectors. For example, in the case of the size |iu4| of the current iu4 and the size |iu5| of the current iu5, the size |iu5| becomes smaller than the size |iu4| because of the influence of a nonlinear characteristic of the hysteresis characteristic. Therefore, making a decision of ranges with 180-degree different phases and uniquely specifying magnetic-pole positions xcex8 based on a simple comparison between the size |iu4| and the size |iu5| has had a problem in that there occurs an erroneous detection of the magnetic-pole positions xcex8.
Therefore, it is an object of the present invention to provide a magnetic-pole position detecting apparatus for a synchronous motor capable of detecting a magnetic-pole position of the synchronous motor easily, securely and in high precision.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor comprising: a circuit unit which applies voltage vectors to an nxe2x88x92 (where n is a natural number of 3 or above) phase winding of a synchronous motor based on a voltage vector command; a detecting unit which detects currents on the n-phase winding generated by voltage vectors applied from the circuit unit; and an arithmetic unit which outputs the voltage vector command to the circuit unit, applies a trigger signal to the detecting unit immediately after an application of voltage vectors based on the voltage vector command, thereby makes the detecting unit detect currents on the n-phase winding, and calculates magnetic-pole positions of the synchronous motor based on the detection currents, and outputs the result of the calculation, wherein the arithmetic unit outputs to the circuit unit the voltage vector command for applying 2n kinds of voltage vectors with equal amplitudes and equal-interval phases to the n-phase winding over the same time period, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the current values of the phases detected by the detecting unit.
According to the above aspect, the arithmetic unit outputs to the circuit unit the voltage vector command for applying 2n kinds of voltage vectors with equal amplitudes and equal-interval phases to the n-phase winding over the same time period, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the current values of the phases detected by the detecting unit. Therefore, it is possible to detect magnetic-pole positions in the precision of xc2x160/(2{circumflex over ( )}(k+1)).
Further, according to a second aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor comprising: a circuit unit which applies voltage vectors to an nxe2x88x92 (where n is a natural number of 3 or above) phase winding of a synchronous motor based on a voltage vector command; a detecting unit which detects currents on the n-phase winding generated by voltage vectors applied from the circuit unit; and an arithmetic unit which outputs the voltage vector command to the circuit unit, applies a trigger signal to the detecting unit immediately after an application of voltage vectors based on the voltage vector command, thereby makes the detecting unit detect currents on the n-phase winding, and calculates magnetic-pole positions of the synchronous motor based on the detection currents, and outputs the result of the calculation, wherein the arithmetic unit outputs to the circuit unit the voltage vector command for applying 2n kinds of voltage vectors to the n-phase winding over the same time period in the order of either a monotonous increase or a monotonous decrease in the phases of the voltage vectors.
According to the above aspect, the arithmetic unit outputs to the circuit unit the voltage vector command for applying 2n kinds of voltage vectors to the n-phase winding over the same time period in the order of either a monotonous increase or a monotonous decrease in the phases of the voltage vectors. Therefore, it is possible to suppress the influence of nonlinear elements like the hysteresis characteristic of the synchronous motor, and it is also possible to detect magnetic-pole positions in high precision.
Further, according to a third aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit outputs to the circuit unit the voltage vector command for applying the voltage vectors, over a time period sufficient enough for the n-phase winding to be magnetically saturated.
According to the above aspect, the arithmetic unit outputs to the circuit unit the voltage vector command for applying the voltage vectors, over a time period sufficient enough for the n-phase winding to be magnetically saturated. Therefore, it is possible to detect magnetic-pole positions in high precision by detecting a change in the inductance due to a magnetic saturation.
Further, according to a fourth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit generates an added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the added current value.
According to the above aspect, the arithmetic unit generates an added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the added current value. Therefore, it is possible to suppress a change in the inductance due to the saliency of the synchronous motor. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to a fifth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit outputs a magnetic-pole position corresponding to the added current value of which absolute value becomes maximum.
According to the above aspect, the arithmetic unit outputs a magnetic-pole position corresponding to the added current value of which absolute value becomes maximum. Therefore, it is possible to detect magnetic-pole positions easily and correctly.
Further, according to a sixth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit outputs magnetic-pole positions corresponding to respective signs of the added current values.
According to the above aspect, the arithmetic unit outputs magnetic-pole positions corresponding to respective signs of the added current values. Therefore, it is possible to detect magnetic-pole positions easily and correctly.
Further, according to a seventh aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit generates a first added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, generates a second added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that have components orthogonal with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the first and second added current values.
According to the above aspect, the arithmetic unit generates a first added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, generates a second added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that have components orthogonal with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the first and second added current values. Therefore, it is possible to suppress the influence of nonlinear elements like a magnetic saturation, and it is also possible to detect a change in the inductance due to the saliency of the synchronous motor. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to an eighth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit generates a first added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, generates a second added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that have components in phase with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the first and second added current values.
According to the above aspect, the arithmetic unit generates a first added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that are in phase with the 2n kinds of voltage vectors, generates a second added current value that is a result of an addition of current values for each combination of every 180-degree different phases from among 2n current values that have components in phase with the 2n kinds of voltage vectors, and calculates and outputs magnetic-pole positions at every 60/(2{circumflex over ( )}k) degrees (where k is a natural number) based on the first and second added current values. Therefore, it is possible to suppress the influence of nonlinear elements like a magnetic saturation, and it is also possible to detect a change in the inductance due to the saliency of the synchronous motor. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to a ninth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit selects a region of a magnetic-pole position corresponding to the first added current value of which absolute value becomes maximum, and specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position.
According to the above aspect, the arithmetic unit selects a region of a magnetic-pole position corresponding to the first added current value of which absolute value becomes maximum, and specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position. Therefore, it is possible to narrow the range of the magnetic-pole position in high precision. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to a tenth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit selects regions of magnetic-pole positions corresponding to respective signs of the first added current value, and specifies a magnetic-pole position by further narrowing each region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position.
According to the above aspect, the arithmetic unit selects regions of magnetic-pole positions corresponding to respective signs of the first added current value, and specifies a magnetic-pole position by further narrowing each region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position. Therefore, it is possible to narrow the range of the magnetic-pole position in high precision. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to an eleventh aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit selects a region of a magnetic-pole position corresponding to the first added current value of which absolute value becomes maximum, specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position, and further specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a new large-and-small relationship that uses the second added current value.
According to the above aspect, the arithmetic unit selects a region of a magnetic-pole position corresponding to the first added current value of which absolute value becomes maximum, specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position, and further specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a new large-and-small relationship that uses the second added current value. Therefore, it is possible to narrow the range of the magnetic-pole position in high precision. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to a twelfth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit selects regions of magnetic-pole positions corresponding to respective signs of the first added current value, specifies a magnetic-pole position by further narrowing each region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position, and further specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a new large-and-small relationship that uses the second added current value.
According to the above aspect, the arithmetic unit selects regions of magnetic-pole positions corresponding to respective signs of the first added current value, specifies a magnetic-pole position by further narrowing each region of the magnetic-pole position based on a large-and-small relationship that uses the second added current value within the selected region of the magnetic-pole position, and further specifies a magnetic-pole position by further narrowing the region of the magnetic-pole position based on a new large-and-small relationship that uses the second added current value. Therefore, it is possible to narrow the range of the magnetic-pole position in high precision. As a result, it is possible to detect magnetic-pole positions in high precision.
Further, according to a thirteenth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit generates a functional current value using a functional value that includes the first or second added current value, and specifies a region of the magnetic-pole position by further narrowing the region based on a large-and-small relationship between the functional current value and the first or second added current value.
According to the above aspect, the arithmetic unit generates a functional current value using a functional value that includes the first or second added current value, and specifies a region of the magnetic-pole position by further narrowing the region based on a large-and-small relationship between the functional current value and the first or second added current value. Therefore, it is possible to extremely narrow the range of the magnetic-pole position. As a result, it is possible to detect magnetic-pole positions in higher precision.
Further, according to a fourteenth aspect of the invention, there is provided a magnetic-pole position detecting apparatus for a synchronous motor of the above aspect, wherein the arithmetic unit calculates and outputs a magnetic-pole position by applying to the n-phase winding a voltage vector sufficiently larger than an induced voltage that is generated by rotation of the rotor of the synchronous motor, during the rotation of the rotor.
According to the above aspect, the arithmetic unit calculates and outputs a magnetic-pole position by applying to the n-phase winding a voltage vector sufficiently larger than an induced voltage that is generated by rotation of the rotor of the synchronous motor, during the rotation of the rotor. Therefore, it is possible to detect magnetic-pole positions in high precision even when the synchronous motor is in rotation.